Definition of tombolo in English:

noun (plural tombolos)

The longshore current can carry large amounts of sand along the coast and can form spits (narrow peninsulas of sand), barrier islands and tombolos (narrow sand deposits connecting a near-shore island with the beach).

You'll just get a cascading series of problems to do with the mechanics of maintaining the tombolo at the same time as having a canal going through it.

The sediments that form tombolos often form in ridges along an underwater wave-cut terrace.